This invention relates to graphite articles and more particularly to graphite articles with increased flexibility.
Graphite sheets are generally made from expanded vermicular particles which are compressed to form graphite-based sheets. Flakes of natural graphite are treated with an acid solution then the treated flakes are exposed to high temperature. This causes the graphite flakes to expand in a direction perpendicular to the crystal plane of graphite atoms (typically referred to in the industry as the xe2x80x9ccxe2x80x9d direction in crystallographic terminology). A form of a substantially flat, flexible, integrated graphite sheet is made by compressing expanded graphite particles which are at least 80 times that of the original particles under a predetermined load and in the absence of a binder. Each particle can be held together without a bonding element. The density and thickness of the sheet may be varied by controlling the degree of compression.
Graphite sheets can be used in many applications because of characteristics such as thermal and chemical stability, low electrical resistivity and low thermal expansion. However, the brittle and relatively low tensile strength of graphite sheets is one of the few disadvantages of the material. Various efforts have been made to improve the graphite sheet strength. One example is laminating a thin film of foreign material between graphite sheets. Although this method results in a sheet that has a higher tensile strength, the brittleness of the graphite is not affected and the material may exhibit cracks on the surface especially when the material is bent or rolled extensively. When graphite sheets are bent or rolled beyond normal handling conditions, cracks are generated on the sheet surface. Such cracks lead to breakage across the sheet. The cracking and breakage are dependent on the thickness of the sheet. Graphite sheets have some degree of flexibility especially with thin sheets (e.g., on the order of 0.03 inch or less sheet thickness). However, graphite sheets lose their flexibility as the thickness and density of the material increases. The thicker and denser the sheet, the more susceptible it is to the generation of cracks when bent or rolled. Because of this property, thick and dense graphite sheets are transported with flat crate packaging which is generally inefficient and not economical. What is needed is a graphite sheet and a method of making a graphite sheet with improved flexibility.
An article of manufacture is disclosed. In one embodiment, the article of manufacture comprises vermicular graphite of a sheet having a texturized surface. In another embodiment, the article of manufacture comprises about 90 to 99 percent graphite and about 1 to 10 percent of a filler (e.g., talc or mica). The article of manufacture may also include an insert in the form of a sheet of, for example, stainless steel, polyester film, or fiberglass fabric.
In another embodiment, a method is disclosed including combining an article having a surface texture with a graphite sheet, and imparting the surface texture to a surface of the graphite sheet.
Additional features, embodiments, and benefits will be evident in view of the figures and detailed description presented herein.